/**
 *    Copyright (C) 2008, 2009  Victor Smirnov <aist11@gmail.com>
 *
 *    This program is free software; you can redistribute it and/or modify
 *    it under the terms of the GNU General Public License as published by
 *    the Free Software Foundation; either version 3 of the License, or
 *    (at your option) any later version.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    GNU General Public License for more details.
 *
 *    You should have received a copy of the GNU General Public License along
 *    with this program; if not, write to the Free Software Foundation, Inc.,
 *    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 *    See LICENSE.exceptions in the root folder of this project for possible
 *    exceptions
 *
 */

#ifndef _CUBEFS_CORE_TOOLS_TYPES_RELATION_PROJECTION_HPP
#define	_CUBEFS_CORE_TOOLS_TYPES_RELATION_PROJECTION_HPP

#include <cubefs/core/tools/types/typelist.hpp>
#include <cubefs/core/tools/types/algo.hpp>

#include <cubefs/core/tools/types/relation/metadata.hpp>


namespace cubefs    {
namespace tools     {

template <typename ColumnType, typename ColumnValue> struct WrapperProvider;

template <Int Name, typename ColumnValue>
struct WrapperProvider<Column<Name, NullType>, ColumnValue> {
    // no wrapper if value is a type
    typedef typename ColumnValue::Value                                         Type;
};

template <typename ColumnType, typename ColumnValue>
struct WrapperProvider {
    // ValueWrapper for constants
    typedef ValueWrapper<typename ColumnValue::Column::Type, ColumnValue::Value> Type;
};


template <typename Metadata, typename ColumnNamesList, typename Record>
class CreateColumnValuesList {

    CUBEFS_STATIC_ASSERT(IsRelationMetadata<Metadata>::Value);
    CUBEFS_STATIC_ASSERT(IsNonemptyList<ColumnNamesList>::Value);

    template <typename Config, typename Column, typename Accumulator>
    struct Handler {
        typedef typename Metadata::template Provider<Column::Value, Record>::Value ColumnValue;
        typedef typename ColumnValue::Column ColumnType;

        typedef TypeList<
                    typename WrapperProvider<ColumnType, ColumnValue>::Type,
                    typename Accumulator::Result
        >                                                                       Result;
    };

    struct Init {
        typedef NullType Result;
    };

public:

    typedef typename ForEach<
                NullType,
                ColumnNamesList,
                Handler,
                Init
    >::Result::Result                                                           List;
};

template <typename Metadata, typename ColumnNamesList, typename RecordList>
class Projection {

    CUBEFS_STATIC_ASSERT(IsRelationMetadata<Metadata>::Value);
    CUBEFS_STATIC_ASSERT(IsNonemptyList<ColumnNamesList>::Value);
    CUBEFS_STATIC_ASSERT(IsList<RecordList>::Value);
    
    template <typename Config, typename Record, typename Accumulator>
    struct Handler {
        typedef typename CreateColumnValuesList<Metadata, ColumnNamesList, Record>::List ValuesList;

        typedef TypeList<
                    ValuesList,
                    typename Accumulator::Result
        >                                                                       Result;
    };

    struct Init {
        typedef NullType Result;
    };

public:

    typedef typename ForEach<
                NullType,
                RecordList,
                Handler,
                Init
    >::Result::Result                                                           List;
};


}
}

#endif //_CUBEFS_CORE_TOOLS_TYPES_RELATION_PROJECTION_HPP